Picture frame



FIG. 1 is a rear perspective view of a picture frame showing my new design;

FIG. 2 is a front perspective view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a front elevational view thereof;

FIG. 5 is a bottom plan view thereof;

FIG. 6 is a side elevational view thereof. 

The ornamental design for a picture frame, substantially as shown and described. 